Help with setting up Mach 3 on EMCO mill

[mouse1942]

Hi guys I picked up a EMCO mill a few years ago and replaced the electrics to bring it into the 21st century. Now the issue I'm having is that I'm loosing steps under load. I have tried all the normal things like slowing down the acceleration and velocity but to no avail. Now i belief its just a tuning issue so would there be someone in the Brisbane area that would like to make a carton if they can tune this thing or at least help in the diagnosis.

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[CNCMAN172]

How big are your stepper motors? Sounds like under a load you are losing steps, so there are a couple of ways to approach this issue. First is get larger stepper motors which have more torque. The second is to provide gearing with pulleys and belts so it takes more revolutions of the motor to move the ball screws which will provide much more torque. There really is no tuning required for stepper motors, if you have servo motors then you have tuning involved. If you have lower the feedrates and decreased your depth of cut and still are losing steps you need to use one of the previous methods to address this issue. Does it lose steps when you do air cuts, if so you need to examine the mechanics of the machine closely you might have some binding occurring, which will cause you to lose steps.

Russ

[mouse1942]

Hi Russ, I purchased these steppers along time ago but from what i can remember they have 380 Nm . They replaced older steppers that where half the size of these. there is also a timing gear reduction on the emco that i kept 40:9 ratio and I'm running them on 2.5 amps. i have run the machine dry using two dials on either side of the head and run it back a forth over 100 times with no step loss. Its also set to 1/8 step.

Dan

[CNCMAN172]

Dan,

If that reduction on both X & Y axis? With that kind of reduction it should be very hard to stall the system. Since your not losing steps when moving back and forth and only running 2.5 amps that seems normal. This could be a driver board issue, you also might try using a different micro step setting like 1/4. Have you tried to move the machine axis without the servos powered do they move easy or can you move them at all with that level of gearing?

Russ

[mouse1942]

Hi Russ , yes the gearing reduction is on both x and y and even on z . when not powered i can wind the gears over smoothly but no i cant push the table. i will try 1/4 stepping and see if that helps. the current setup should allow me for a crazy amount of micro stepping thats a bit over kill.

Dan

[CNCMAN172]

YES, I agree with that level of gearing you don't need a great amount of micro stepping. Give the 1/4 micro stepping and see if anything changes. The fact that you can rotate the rears and it all moves smoothly is perfect. This sounds like a driver issue and some drivers have much reduced torque with high levels of micro stepping. This will be a good test.

Russ

[janders57]

When you did your dry run back and forth testing, was the spindle running? What is powering your spindle?
Just wondering if maybe you might have an electrical interference issue, electrical noise when the
spindle is running picked up by the drivers and generating extra steps.

Jon

[RCaffin]

I purchased these steppers along time ago
A LONG time ago? Are they square or round?
I have a drawer full of lovely old round steppers of various sizes. All in very good condition - EXCEPT that the ferrite magnets in them have all died. The motors will spin with no load, but they can't drive anything. No torque. This is apparently what happens to the round motors.

Power up a motor and start it turning. Can you stop it by hand?

Cheers
Roger

[mouse1942]

OK so i have tried dropping the steps down to half step with no change it still skips steps. I know I'm loosing steps because it cuts over size if i cut a OD or under size if i cut a ID. Jon the spindle is running off a separate 240v driver dropping it from 240 AC to 180 DC and yes i have run the spindle with it cutting very light material and it cuts fine. It just cant handle it when i amp up the load a little and when i say little i mean cutting aluminium at 3mm depth of cut with a 1mm step over on a 10mm 4 flute solid carbine cutter at 2500rpm. I'm thinking its the drives i have, they are Hy DIV 268 3A. So i will change them out for one of those 3 in 1 gecko drives. I have been thinking this for a bit but wanted to ask the question first.

[RCaffin]

when i say little i mean cutting aluminium at 3mm depth of cut with a 1mm step over on a 10mm 4 flute solid carbine cutter at 2500rpm.
Um. On an EMCO? I would not call that 'little' myself. With servo drives maybe, but steppers?
Are you climb milling or conventional milling?
And are they round or square motors?

Some things to try: DoC of 1 mm, 6 mm cutter, climb milling.

Cheers
Roger

[mouse1942]

They are square steppers. I have tried both climb and conventional. The dia of cutter is irrelevant considering I'm only talking about side load not end load. Yes i could try a 1 mm depth of cut but i really think this machine should be able to do better. i have cut deeper than that and it sounds and machines well except it skips steps.

[RCaffin]

machines well except it skips steps
It's a problem.

Have you checked the dovetails for drag? If it flies back and forth with no problems when not cutting or only cutting lightly, it may be that the grease has gone a bit solid over the years and the sideways cutting forces are causing too much drag. Just a thought.

Cheers
Roger

[mouse1942]

Yep that was my first port of call , i have pulled the table off and cleaned and re oiled it.

[RCaffin]

Um. I am running out of ideas.
Bigger hammer?
You could consider a conversion to 300 - 500 W DC motors with encoders and servo drives & a 3:1 toother belt reduction. That's what I use.

Cheers
Roger

[mouse1942]

Bugger lol oh well i think it will sell it before i go that far although i did want it going before i did this. Its to small anyway really for what i want to do every job i go to put on it is too big or to tall. Would you be in Brisbane at all for me to have a look at your setup or post some pictures of it.

[RCaffin]

Sorry - in Sydney.
I have an Adept VMC, bought from the Bliesners at the AdeptCIMCentre in Qld. It's not large but has good height, and is extremely robust.
They were built for the NSW Edu market, but no-one thought to check about trained CNC teachers. So a lot of machines sat there for 10+ years doing nothing. They are 'student-proof' in strength, really! The Bliesners buy them cheap from the schools and replace the electronics with modern stuff, plus Mach3. But they are not cheap.

Mine has been enhanced a bit: full air blast + pulsed misting, touch probes, and a new electronics layout with LOTs of meters etc. Encoder resolution is 0.8 microns, zero-setting is to about 5 microns, working to 0.01 mm is routine.

Cheers
Roger

[CNCMAN172]

Mouse1942,

Cutting aluminum with a DOC of 3mm on a home machine is pretty tough unless you have a powerful spindle and a very stiff machine. That is 0.118" using the USA standard. Now even on a Bridgeport that can be done but they are very heavy and stiff and typically had 3-5HP motors.

Russ